New methods of finishing help speed post processing of 3D printed objects.
Edited by Leslie Langnau, Managing Editor
As capable and useful as 3D printers/additive manufacturing (3DP/AM) machines are, one issue is that no 3D printer, no matter what size, style or resolution, can produce objects with the same level of surface quality as traditional manufacturing methods. No matter how well designed an object is or how advanced the printer is (at present), the basic nature of 3D printing will not allow for the same uniform surface that injection molding or CNC machining provides.
Fortunately, there are steps you can take to give the object the look and feel of one produced through other means. These steps can be as simple as sanding an object down by hand or as complicated as electroplating. Regardless of the method used, the goal is to make the 3D-printed part look and feel as close to the finished product as possible.
The material typically used in Fused Deposition Modeling (FDM) and some Fused Filament Fabrication (FFF) systems is similar to materials used in many industries. Petroleum is the base material in most polymers.
There are several ways to remove excess and support material, with new methods emerging constantly. For parts with excess material on the outside, the usual method is to simply snap off, or break off, the excess material.
For parts with excess material inside the part, the typical method is to use dissolvable support material. After the part has been printed, it is placed in a tub of dissolving solution that liquefies the support material, leaving only the finished part. Depending on the 3D printer manufacturer, this solution may require special handling in terms of ventilation, gloves or other equipment.
A new method uses the laws of Physics to turn conventional automated systems commonly found in mainstream manufacturing into effective FDM/FFF finishing systems. A redesign of the conventional wash cabinet creates a physical action and energy that will dissolve FDM/FFF soluble support in a way that is similar to that used to dissolve heavy greases and tallows. For example, if you take two large ice cubes and drop one in standing hot water, it will take up to ten minutes to dissolve. But if you take the other ice cube and hold it under running hot water, the water temperature and the physical action (running water) dissolves the ice cube in seconds.
A new type of wash cabinet was modified using these ideas. Instead of a spray, up to 20 gallons of water per minute under low psi floods the cabinet from all directions. Any FDM/FFF support material is removed in minutes. In addition to support removal, these cabinets can be designed to wash and dry for production applications.
Another method that takes advantage of conventional systems is vibratory finishing. This method has been used in many industries to smooth surfaces, polish and burnish part surfaces. In mainstream manufacturing after a part has been designed and manufactured, it is tested in a vibratory finishing system to determine if it comes out sufficiently smooth and polished. The results are documented and the process repeated to determine if the process can be repeated for consistent quality.
These methods should be the same for Direct Digital Manufacturing (DDM). These steps are critical for production results and to maintain consistent quality and repeatability. Even though working with polymers is different than metal or woods, the same conventional methods can be as effective.
Vibratory finishing for polymers can be a one-step or two-step process to get a part ready for paint. The part surface can also be deformed for an injection-molded look. As in mainstream manufacturing these parts may need special fixtures or masking to protect areas of the part. By reverse engineering these are easily achieved for FDM application.
The automation of conductive paint and coatings is probably the last process in the production line for FDM. The addition of conductive material to the polymer parts is a fast and effective process for finished parts. n MPF